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The latest in a series of experiments testing the ability of robots to influence live animals shows that bio-inspired robots can not only elicit fear in zebrafish, but that this reaction can be modulated by alcohol. These findings may pave the way for new methodologies for understanding anxiety and other emotions, as well as substances that alter them.

Maurizio Porfiri, associate professor of mechanical and aerospace engineering at NYU-Poly, and Simone Macrì, a collaborator at the Istituto Superiore di Sanità in Rome, Italy, published their findings in PLOS ONE.

This latest study expands Porfiri and Macrì’s efforts to determine how bio-inspired robots can be employed as reliable stimuli to elicit reactions from live zebrafish. Previous studies have established that zebrafish show a strong affinity for robotic members designed to swim and appear as one of their own, and that this preference can be abolished by exposing the fish to ethanol.

Porfiri and Macri, along with students Valentina Cianca and Tiziana Bartolini, hypothesized that robots could be used to induce fear as well as affinity and designed a robot mimicking the morphology and locomotion pattern of the Indian leaf fish, a natural predator of the zebrafish. They simulated a harmless predatory scenario, placing the zebrafish and the robotic Indian leaf fish in separate compartments of a three-section tank. The other compartment was left empty. The control group uniformly avoided the robotic predator, showing a preference for the empty section.

To determine whether alcohol would affect fear responses, the researchers exposed separate groups of fish to different doses of ethanol in water. Ethanol has been shown to influence anxiety-related responses in humans, rodents, and some species of fish. The zebrafish exposed to the highest concentrations of ethanol showed remarkable changes in behavior, failing to avoid the predatory robot.

The researchers say robots are ideal replacements as independent variables in tests involving social stimuli: They are fully controllable, stimuli can be reproduced precisely each time, and robots can never be influenced by the behavior of the test subjects.

To validate their findings and ensure that the zebrafish behavior being modulated was, in fact, a fear-based response, Porfiri and his collaborators conducted traditional anxiety tests, simulating a heron attack from the water’s surface; herons also prey on zebrafish.

Porfiri and his colleagues believe zebrafish may be a suitable replacement for higher-order animals in tests to evaluate emotional responses.

This research was supported by the National Science Foundation, the Honors Center of Italian Universities, and the Mitsui USA Foundation.